1. Field of the Invention
The present invention relates to a color cathode ray tube used for a television receiver and a computer display.
2. Related Background Art
In recent years, in order to reduce reflections and provide a good appearance, a color cathode ray tube having a substantially flat face panel for displaying an image is becoming mainstream. Following this, a shadow mask that is disposed inside of the tube so as to oppose an inner face of the face panel tends to be supported in a state closer to a flat form than before. As the supporting method, a tension method is known in which a shadow mask is welded and fixed to a frame while applying tension to the shadow mask.
In the color cathode ray tube employing the tension method, various measures are taken for preventing color displacement generated due to vibration of the shadow mask, which is caused by the transmission of vibration of a speaker or the like. For example, JP 2001-101978 A discloses a technology for attaching a vibration damping member, which is formed in a frame form by bending, to a shadow mask so that the vibration damping member can move freely.
According to this technology, when the shadow mask vibrates, the vibration damping member moves independently of the shadow mask. As a result, the vibration energy of the shadow mask is converted into a friction energy between the vibration damping member and the shadow mask to be consumed, thus dampening the vibrations of the shadow mask. Also, such a vibration damping member can be formed easily and accurately.
However, the frame-form vibration damping member described in this prior art has the following problem: this vibration damping member exerts remarkable effects for suppressing the vibrations of the shadow mask if the vibration damping member always can be kept in a freely movable state. In this respect, as shown in FIG. 11, a bending portion 32a or 32b of a vibration damping member 31 tends to be caught by the edge of a mounting aperture 33 in the shadow mask 5, and once the vibration damping member 31 is caught so as to be pinned (i.e., latched and fixed) by the shadow mask 5, then it becomes impossible for the vibration damping member 31 to return to a freely movable state. This means that the effective vibration damping for the shadow mask 5 may not be achieved.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a color cathode ray tube in which vibration of a shadow mask is dampened effectively by providing the color cathode ray tube with a vibration damping member attached so as to always keep a freely movable state.
In order to fulfill the above-stated object, a color cathode ray tube of the present invention has the following configurations.
That is, a color cathode ray tube according to the present invention includes: a shadow mask held in a state of tension applied thereto; two mounting apertures provided in the shadow mask or a different member attached to the shadow mask, the different member vibrating following vibration of the shadow mask; and a vibration damping member penetrating through the two mounting apertures to be attached in a freely movable state to the shadow mask or the different member, the vibration damping member dampening vibrations of the shadow mask.
In a first color cathode ray tube of the present invention, the vibration damping member has two penetrating portions each passing loosely through one of the two mounting apertures and a bridge portion linking the two penetrating portions. A protrusion or a swelling portion protruding toward the shadow mask or the different member is provided in the bridge portion.
In a second color cathode ray tube of the present invention, a protrusion or a swelling portion protruding toward the vibration damping member is provided at a region between the two mounting apertures of the shadow mask or the different member.
A third color cathode ray tube of the present invention further includes a member that has an aperture through which the vibration damping member penetrates and is attached in a freely movable state to the vibration damping member.
In a fourth color cathode ray tube of the present invention, the vibration damping member has two penetrating portions each passing loosely through one of the two mounting apertures, and the vibration damping member has an asymmetrical shape with respect to a center position between the two penetrating portions.